Associations may exist between obesity and adverse health conditions related to service in the Gulf War such as post traumatic stress disorder (PTSD), chronic fatigue syndrome (CFS), and unexplained multi-symptom illness (MSI) [9–13]. For example, PTSD has been associated with obesity and metabolic syndrome in selected veteran populations [13, 14]. However, previous studies have not studied the relationship between obesity and PTSD in nationally representative populations of veterans, while adjusting for multiple potential confounding factors. The biological pathways that underlie these associations may relate to the hypothalamic-pituitary-adrenal axis and biological responses to chronic anxiety and stress. Studies of CFS in U.S. populations have suggested that CFS is heterogeneous and includes subgroups of patients who are obese [15, 16].

We analyzed data from a follow-up health survey among population-based samples of 15,000 Gulf War veterans and 15,000 veterans who served during the same era. Data were collected from 9,970 respondents in 2003–2005 via a structured questionnaire or telephone survey. The objective of this analysis was to examine the frequency of PTSD, CFS-like illness, unexplained MSI, and selected health conditions among Gulf War and Gulf Era veterans who were underweight, normal weight, overweight, or obese.

Table 2 shows the percentages of Gulf War or Gulf Era veterans who had the health condition of interest by particular BMI categories (underweight, normal weight, overweight, or obese). Without adjustment for Gulf deployment status (Gulf War vs Gulf Era), age, sex, or other factors, PTSD, MSI, CFS-like illness were more common among obese veterans than those who were normal weight (BMI 18.5 to ≤ 24.9). Several other chronic health conditions were also more common among veterans who were obese, including depression, coronary heart disease, arthritis, diabetes, and hypertension (Table 2). Veterans who were obese were also more likely to report a functional impairment or limitation of activities. Self-reported hypertension that had been diagnosed by a doctor was more common among overweight veterans than those who were normal weight (Table 2). About 41.5% of underweight veterans had been told by a doctor that they had depression and 48.8% of those who were underweight had unexplained MSI (Table 2).

The specific exposures that account for increased risks of MSI and CFS-like illness among Gulf War Veterans are unknown but may include environmental factors such as pyridostigmine bromide or exposure to certain pesticides [23]. Many of the troops were exposed to a wide array of wartime and environmental exposures including psychological stress, solvents, fuels, and pesticides, pyridostigmine bromide pills given to protect troops from effects of nerve agents, smoke from large numbers of oil well fires, and multiple prophylactic vaccines given to protect against anthrax and other infectious agents. Some troops were also potentially exposed to low-level sarin or other nerve agents as a result of the burning of munitions dumps. Multiple exposures often occurred and the effects of two or more combined exposures (for example, mixtures of respiratory irritants such as oil smoke and fuel combustion products and combinations of neurotoxic substances such as certain pesticides and low-level nerve agents) may have potentiated each other [23].

A further issue is that the cohort of Gulf War veterans is advancing in age and these veterans are likely to be at increasing risk of not only certain deployment-related health conditions but also chronic diseases associated with “lifestyle factors” (e.g., physical inactivity and a high caloric or high fat diet). An increasing number of studies have identified overweight and obesity as important health concerns among U.S. veterans of various ages [1–5]. Important associations may exist between obesity and adverse health conditions related to service in the Gulf War such as PTSD [10–13]. Persons with PTSD or depression may be less likely to remain active or to eat a healthy diet. Dietary information was not collected in the current study. Possible biologic pathways for a link between PTSD and obesity may involve the hypothalamic-pituitary-adrenal axis and metabolic changes that occur as a result of chronic anxiety or stress. Taking into account evidence from studies conducted in the general population, veterans who are overweight or obese are likely to be at increased risk for adult-onset chronic diseases such as coronary heart disease, diabetes, hypertension, arthritis, and several forms of cancer [6–8]. Long-term follow up studies of the persistence of PTSD, CFS-like illness, and unexplained MSI, among Gulf War veterans must be conducted in the context of changing risks of chronic diseases that occur among both veteran and non-veteran populations as people get older. Although reverse causation is often an important consideration in studies of comorbid health conditions, all of the men and women included in the current study had to have been physically fit at the time they entered military service. The military has weight limits based upon height, weight, and sex. Each branch of the military has its own body composition standards. Persons with certain health conditions are excluded from military service. Military service itself is often physically demanding. As a result, veteran populations such as those who served in the 1991 Gulf War are not comparable to persons in the general population. The current study provides important new information about comorbidity between obesity or overweight and other important veterans health concerns such as PTSD, CFS-like illness, and unexplained MSI. Although there was some indication that BMI modified the effect of CFS-like illness on PTSD, obesity was an important comorbid health condition among both deployed and nondeployed veterans with CFS-like illness or PTSD.

The troops who served in the 1991 Gulf War were exposed to many stressors including rapid mobilization, wartime hostilities, and concerns about potential chemical attacks. These and other war-time exposures (for example, witnessing deaths or being exposed to hostile fire) may have led to PTSD among some of these veterans). PTSD may lead to other adverse health outcomes and conditions. In previous studies, PTSD has been associated with obesity, metabolic syndrome, and other CHD risk factors in veterans [13–14]. In the current study, PTSD was positively associated with obesity after adjustment for age, sex, Gulf status, and other factors. Although the direction of the association cannot be determined from this cross-sectional analysis of data from the 2003–2005 follow-up survey, it is possible that veterans with PTSD are more likely to consume a high caloric diet or less likely to exercise. This is speculative, however, since the current study lacked data on diet or physical activity.

With respect to other limitations of the current study, exposures such as body mass index and weight were based upon self-reported information. However, studies conducted in non-veteran populations have suggested that the reliability and validity of self-reported information about height and weight obtained in large-scale epidemiologic studies are reasonably good [24]. Estimates of BMI obtained from self-reported information are more accurate among persons less than 55 years of age than those 55 or older and may also vary by gender and ethnicity [25]. A further issue is that estimates of weight may be preferable to BMI for assessing over-weight since weight-for-height indices may not adequately distinguish between adipose individuals and those who are heavily muscled [1]. Response bias is also a possibility in view of the response rate of 34%. In a previous analysis of these data, Kang et al. [18] compared characteristics of respondents and nonrespondents, stratified by Gulf deployment status. In both Gulf War veteran and Gulf Era veteran groups, nonrespondents were more likely to be younger, non-white individuals who served in enlisted ranks at the time of the 1991 Gulf War. In addition, Gulf War veteran participants were more likely women and on National Guard or reserve during the Gulf War service than Gulf War veteran nonparticipants [18].